Conventional tube lamps (fluorescent lamps) of the type having a two-pin connector at each end of the tube are, in steady-state operation, powered by a DC or AC electric current flowing between the connectors. The connectors are electrically disconnected until an arc has established in the tube. For this purpose, a starting procedure including preheating of the electrodes may be carried out by dedicated starting circuitry, which can be made inherently safe by being enabled only when the lamp is properly inserted into the fixture, so that live electric parts are always protected from touch. The starting circuitry may be of the switch-start/preheat, rapid-start or other type, and is commonly integrated in the fixture.
It is desirable to power a tube lamp retrofit in the same manner as the tube lamp it replaces, that is, by a current flowing between its end connectors. Depending on the internal circuitry of the lamp, potentially hazardous conditions may arise when the lamp is partially inserted or partially removed from the lamp fitting. Among the attempts to solve this problem, WO2009/067074 proposes a light emitting diode (LED) tube lamp having a power switch which is arranged to close the lamp circuit when two ends of the lamp simultaneously are inserted into the respective contact sockets. The power switch has two pressing members, which are arranged on each side of the contact pins. If the tube lamp is inserted slantingly into the contact socket, the power switch is actuated only by one of the pressing members, whereby a safety arrangement of guiding pins, grooves and stop heads prevents the power switch from closing the circuit. However, such a safety arrangement is technically rather complex.